Aqueous media containing metal ions arises from many processes. For example, such aqueous media can arise as a byproduct from producing titanium dioxide by the chloride or sulfate process; cleaning or etching steel, iron or other metals with acids; leaching various ores with mineral acid; and treating or plating metals.
Large quantities of such aqueous media exist. Often, to dispose of them, they are deep-welled or neutralized with a basic material such as calcium oxide, sodium carbonate, calcium hydroxide, dolamite, sodium hydroxide or potassium hydroxide. Traditionally, the resulting solids have been landfilled and the resulting brine has been deep-welled or discharged to surface waters. These methods, however, are becoming less viable because environmental requirements are becoming more stringent.
The need therefore exists for a process for treating aqueous media containing metal ions that would produce saleable products and thus would reduce use of landfills and other disposal methods.
The following brief summary is provided of certain references that may be pertinent to this invention.
Wentzler, U.S. Pat. No. 5,039,428, discloses a process for removing dissolved metals from waste water by treating with sodium hydroxide or calcium hydroxide to form precipitates, and recycling a portion of the precipitates.
Kostenbader, U.S. Pat. No. 3,738,932, discloses a process for treating acid water containing metallic values with an alkali-water slurry and recycled sludge mix to neutralize the acidity and precipitate the metallic values as solids.
Gaughan, U.S. Pat. No. 3,575,853, discloses a process for treating waste water comprising reducing the metal ions therein to their lowest valence state, treating with an alkali media to form precipitates, and recycling a portion thereof after settling.
Herman, U.S. Pat. No. 4,465,597, discloses a process for remediating acidic waste water containing dissolved heavy metals and having a pH of about 2.5-5 by treating with a carrier agent and neutralizing agent.